This invention relates to a process for preparing formed polycaprolactam bodies which are rendered self-extinguishing by incorporating red phosphorus in powder thereinto.
As is known, polycaprolactam (hereinafter referred to as PCL) is a thermoplastic aliphatic polyamide, usually called Nylon-6, which is widely used, due to its excellent physical and mechanical properties, in various technical fields, from that of fibres to one of the components for the electrotechnical and automotive industry.
Nevertheless, the utilization of PCL finds considerable limitations and hindrances in those fields of use for which risks of fire exist, namely in relation to the inflammability and to the easy flame propagation of PCL.
It is known that PCL can be rendered self-extinguishing by a process contemplating first the preparation of a mechanical mixture of granules of PCl and of a suitable flame-retardant, and, successively, the incorporation of said retarding agent into PCL by plastic melting-mixing of the abovesaid mechanical mixture in screw extruders operating at temperatures above 230.degree. C., thereby obtaining self-extinguishing PCL granules. Such granules, in order to be transformed into formed articles, must be then melted again to the plastic state, always at high temperatures, for example in presses for the injection molding of finished articles, and in extruders for the forming of structural shapes and the like.
The above process, as is apparent, is affected by the drawbacks of requiring high consumptions of energy, of causing, due to the action of heat and of friction, undesired modifications in the distribution of the PCL molecular masses (and, by consequence, in the physical and mechanical properties of PCL), and, finally, of not obtaining the optimal distribution of the flame retarding agent in the body of the PCL finished article.